1. Technical Field
The present invention relates to a device for loading and unloading a machining machine for machining boards.
2. Background Information
The term “board” as used here is understood in general to refer to a relatively thin flat object made of a solid material (e.g., metal, stone or wood).
In industrial manufacturing, devices and methods for machining boards are used in a variety of ways, e.g. for cutting, coating or machining surfaces of boards. To achieve a high productivity, automatic machining systems are generally used, including not only a machining machine for boards but also an automatic device for loading and unloading the machining machine.
Known devices for loading and unloading usually includes a storage system which includes a first storage place for boards to be machined and a second storage place for the boards machined by the machining machine, and a conveyance device for conveying the boards to be machined and for conveying the machined boards between the storage system and the machining machine.
The conveyance device usually includes at least one changing table on which a board to be machined or a machined board may be situated, whereby the respective changing table can be conveyed between the storage system and the machining machine for conveyance of the boards along one or more predetermined paths.
The respective changing table is usually brought to a predetermined loading place for loading with boards. For automatic loading, a loading device is usually provided, designed to remove a board for machining from the first storage place and depositing it on the respective changing table at the loading place. Accordingly, a changing table loaded with a machined board may be unloaded at a predetermined unloading place. For automatic unloading, an unloading device is usually provided, designed for removing a machined board from the respective changing table at the unloading place and depositing it at the second storage place.
In the design of automatic machining systems, several optimization criteria are usually taken into account. First, the machining machine should achieve a high throughput of boards. Secondly, the machining system should take up the least possible amount of space, e.g., with regard to the required floor space and/or height in a room. In addition, the conveyance device should ensure a conveyance capacity (high) adapted to the throughput of the machining machine in the simplest possible manner (the conveyance capacity being characterized, for example, as the number of boards conveyed per unit of time between the machining machine and the respective storage places).
To allow a high conveyance capacity, a machining system is usually equipped with multiple changing tables which can circulate simultaneously between the machining machine and the respective storage places along predetermined paths. For example, it is therefore possible to load a changing table (empty) with a board for machining, while another board—lying on another changing table—is being machined by the machining machine or a board that has already been machined is moved away from the machining machine in the direction of the storage system.
To facilitate circulation of multiple changing tables between the machining machine and the storage system, automatic machining systems are usually provided with a so-called changing table changer. A changing table changer is usually a device includes at least two different guide paths for changing tables, whereby the guide paths are designed so that a changing table to be conveyed between the storage system and the machining machine may optionally be moved along at least one of the respective guide paths of the changing table changer. Conventional changing table changers make it possible, for example, for a first changing table to assume a place on a guide path of the changing table changer while another changing table is moved past the first changing table in a predetermined direction along another guide path. The changing table changer makes it possible, for example, for several changing tables to be moved between the machining machine and the storage system in opposite directions without any mutual hindrance.
Typical machining systems are usually designed so that a changing table can be loaded and/or unloaded when the changing table assumes a place on the changing table changer, i.e., in this case the loading place and the unloading place of the changing table are each situated directly in the area of the changing table changer.
To largely reduce the floor space required by the machining system, the storage system may be designed, for example, so that the respective storage places for the boards to be machined and the boards that had been machined are arranged one above the other.
With regard to the arrangement of the changing table changer in relation to the machining machine and the storage system, several variants are usually taken into account. The changing table changer may be arranged, for example, next to the storage system, e.g., in an intermediate space between the machining machine and the storage system. According to another variant, the changing table changer is arranged in the same plane with the machining machine, the storage system being arranged directly above the changing table changer. The latter variant has the advantage over the variant mentioned previously that the changing table changer and the storage system jointly take up a particularly small amount of floor space, but it also has the disadvantage that the changing table is not readily accessible (because of the arrangement of the storage system).
For the case when the respective loading place and the respective unloading place for the boards are provided on the changing table changer, the two variants mentioned above have the disadvantage that boards must be moved both horizontally and vertically in both loading and unloading a changing table over relatively long paths which often involve curves. For this reason, conveyance of the boards between the loading place and/or the unloading place and the respective storage places is associated with complicated movements of the boards, usually in three dimensions. The designs of the loading device and/or unloading device are complicated accordingly. In addition, this requires a complicated control of the movement processes.
Another disadvantage may be regarded as the fact that the loading and unloading of changing tables may be time-consuming if the loading place and the unloading place of the changing tables are each provided at the place of the changing table changer, i.e., essentially at the same location. In this case, multiple changing tables cannot be loaded and/or unloaded at any points in time, for example, because the conveyance of the changing tables, the boards to be machined and the boards that had been machined must be coordinated accordingly. Simultaneous loading and unloading of various changing tables are usually impossible. This has a negative effect on the conveyance capacity of the conveyance device.